JDS Labs is already selling the completed board for $99 US and board+case for $144 US. I think you could offer both the case by itself and a complete amp in the case. As long as credit is given, I'm sure there's a market for it.

Check that C8 and C9 are in the right way. The (-) side should go towards the input jack.

No, the volume control doesn't have any effect on that. It's all very weird, really. I don't think I've got the caps reversed or I'd have smoked them a long time ago Anyway, even if I did, how would that couple the signal to the output all of a sudden?

JDS Labs is already selling the completed board for $99 US and board+case for $144 US. I think you could offer both the case by itself and a complete amp in the case. As long as credit is given, I'm sure there's a market for it.

I intend to give full credit for the AMP, i would have only put it together, the thing is if I aim for a high end market for the cases I would expect people will also want me to match the internals to the case. In other words , the best case I can build coupled to the best amp I can afford / can buy.

No, the volume control doesn't have any effect on that. It's all very weird, really. I don't think I've got the caps reversed or I'd have smoked them a long time ago Anyway, even if I did, how would that couple the signal to the output all of a sudden?

For the input signal to make it through to the output without power, given the common ground, it would pretty much have to either punch through the signal path, or out to the power supply rails via the internal circuitry of the op amp(s).

No change from the volume control should rule out the signal path. The power supply bypass capacitors C8 and C9 should also do an effective job at bypassing any signal current on the supply rails, leaving just whatever voltage results from signal current x capacitor series resistance.

And it's not like we intend to rip anybody off.
(I can really only speak for myself, but you get the point.)

If someone offers a service and performs according to the agreement, then this is not ethically questionable.
My hourly wage at work is FAR higher than what I make from the GB.
And I put nearly all of it back in, buying components before they are ordered (like the 500 PCBs).

And this holds true for most people in this community.
When Mr Slim offered the build-service, there were lots of people very happy to have him assemble their O2s.
He charged something for the services rendered, but again, it was a very reasonable amount.
For someone who doesn't own a soldering iron, his service was likely cheaper than a semi-decent iron.
So some people saved money using his service, just like 'my' buyers save money.

And as long as we propagate a good and productive spirit throughout this community, we provide it with a very strong incentive for others to join.
I know of several people that joined DIYaudio specifically for my GB and then stayed and participated in a variety of other discussions.
This is a good thing. At least in my book. And I have absolutely no problem with anybody that begs to differ.
I am paraphrasing: We are free citizens. We can do what and when we please. And we don't even have to do THAT!

Best regards,
Jokener

P.S.: I had lengthy conversations with RocketScientis on many topics.
He explicitly told me that he would be pleased to see me make a 'nice little profit' from my GB's.
And even though this was about my GB, his attitude towards any good-spirited person offering a service for and around the O2 will most certainly be identical.

P.P.S.: I would also very much like to see a 'donation box' for RS.
That way anybody could buy him a pint for his great work and spirit.
Wait, scrap that. With that amount of beer, he would end up an alcoholic.

RS clearly made a deliberate decision when he chose the Creative Commons License. That means he specifically released the amp "into the wild" with a few clearly stated caveats (for example attribution, and don't distribute a derived work while calling it an O2). There is nothing immoral nor illegal about selling O2's in any state from bare PCB to complete product, as long as the conditions of the License are adhered to (including informing down-stream users of their rights and responsibilities).

Read the License, understand what it says, and you will have no problems.

You guys are right about this, I just hope the cases are the focal point as we all know that soon there will be O2 clones from china , doubt someone is going to hold a sustainable business soldering O2's. I heard they have a smaller version PCB with two 18650 Li-ion batteries 2500mah each (so 9V for much longer time) dc adapter, no AC and a desktop version with higher rails dip heatsinking and one of Ti's 32 bit DAC's. There is always seems to be a market for quality custom cases, the market for headamps especial low parts cost ones like is so competative, keep it fun , I don't mix business with pleasure. And each day the O2 becomes more pleasureable , hate to say it but until real headphone output transformers are available tubes are losing interest for me thanks to the O2. I never realized what I was missing below 30 hz, the distortion and level below 40hz from the O2 is really going to be tough to even come close to with tubes. The O2 is like a splash of cold water in the face in a way, but listening to electric bass and drums with this clarity is quite amazing.

P.P.S.: I would also very much like to see a 'donation box' for RS.
That way anybody could buy him a pint for his great work and spirit.
Wait, scrap that. With that amount of beer, he would end up an alcoholic.